In recent years, in view of energy saving and environmental conservation, illumination apparatus (such as LED bulbs and LED fluorescent tubes) using a light-emitting diode (hereinafter also referred to as “LED”) as a light source have been increasingly replacing electric light bulbs and fluorescent tubes. In generally used LED fluorescent tubes, a plurality of LEDs are disposed on a substrate at a predetermined interval, and a cover is disposed so as to cover the LEDs (see, for example, PTL 1).